1. Field of the Invention
A dual pneumatic actuator gate or door closer.
2. Description of the Prior Art
Numerous gate and door closer designs have been developed over the years. These designs include pneumatic closers with pneumatic cylinder/piston arrangements.
Typically a cylinder is disposed in a chamber for compressed air to enter and a path for the air to leave and a piston with some type of action system. There are several different types of action systems for pneumatic cylinders each providing a slightly different kind of force. The first and most simple version is the single acting cylinder, where a piston oriented system forces compressed air through a solenoid valve into the back of the piston. This highly compressed air seeks the easiest way to exit and exerts a force on the piston face. As the piston is pushed out the air exits through escape valves positioned further down the cylinder. The piston falls back naturally in place until another burst of compressed air is fired into the cylinder.
The single acting cylinder can also be modified with a compressed spring mechanism, inserted between the end of the cylinder and the side of the piston opposite where the compressed air enters. This system works in a similar fashion but after the compressed air is released, the piston is forced back down to its original position at the end of the cylinder by the spring. This system is used for repeated linear motion involving heavy loads and requires a greater force of compressed air to complete cycle.
Pertinent examples of various designs are set forth below.
U.S. Pat. No. 369,203 and U.S. Pat. No. 1,190,563 disclose a door closer employing a single spring to return a door to the closed position after being extended or stretched by applying mechanical force to opposite ends thereof when opening the door.
U.S. Pat. No. 4,935,989 shows a door closer of the cylinder/piston type pivotably mounted to a door at a point adjacent the piston rod end of the cylinder. A leaf type spring may be added between the cylinder and the door. This configuration increases the closing force to the door as the door closes.
U.S. Pat. No. 5,471,708 describes a pneumatic door closer including an elongated cylinder with a bore extending axially thereof and end walls and a piston slidably reciprocable within the bore. A sealing ring of resiliently deformable material is disposed in a groove with greater diameter than the piston so as to project outwardly thereof. Since the axial dimension of the groove increases radially outwardly to a dimension greater than the diameter of the ring, the ring may move axially therewithin. When the piston moves toward the door closing position, the sealing ring bears against the diverging wall surface of the groove and the wall of the cylinder to restrict flow of air and when the piston moves towards the door opening position, the sealing ring bears against the generally radially extending wall surface of the groove to permit flow of air thereby.
U.S. Pat. No. 4,920,609 relates to a door closer comprising a housing, a plunger rod in the housing with a plunger at the inner end of the rod and a main spring disposed around the rod between the plunger and a housing end for urging the rod into the housing. With the door closer connected to a door, an actuator slides into a latch space when the door has been opened to hold the door open. A further opening movement raises the actuator out of the latch space and a sleeve maintains the actuator raised, permitting closing of the door.
U.S. Pat. No. 6,317,922 shows a door closer includes a cylinder and a piston sliding along the cylinder. The door closer has a speed adjustment knob extending from a first end for varying the closure rate. A door lock maintains the piston in an extended position and keeps the door open. The lock includes a washer sliding on the piston rod in a first position and locking the rod at a second position. The washer has a tab that engages an angled surface in the first position to prevent locking engagement with the piston rod. A rotatable end cap rotates the washer between the locked position and the unlocked position.
U.S. Pat. No. 8,051,534 relates to a pneumatic door closer comprising an elongated cylinder with a displaceable piston defining a vacuum chamber and a pressure chamber within the elongated cylinder wherein the piston is normally biased toward a door closing position by bias or spring. A piston rod connected to the piston has its free end extending through a rod opening that includes an air impervious seal formed about the piston rod extending therethrough. Disposed in communication with the vacuum chamber is a breather arrangement for diminishing in a controlled manner the level of vacuum being created within the vacuum chamber during the closing stroke of the piston to control the resulting resistance forces acting on the piston such that the closing speed is essentially uniform throughout the closing stroke.
Additional examples of the prior art are found in U.S. Pat. No. 1,286,664; U.S. Pat. No. 2,198,402 and U.S. Pat. No. 2,969,560.
While some of the prior art may contain some similarities relating to the present invention, none of them teach, suggest or include all of the advantages and unique features of the invention disclosed hereafter.